I was writing a JSP web app using a custom tag library I found in a book where there a template framework would separate data and layout of the page. A JSP page would look like the following :
<region:define template='some_template.jsp'>
<region:region section='content' name='content.jsp'/>
</region:define>

So, one day our tester opened two different browser window on her computer and logged in as two different users. Everything went fine until she went into one page where there's this following code (not complete but you get the idea):

<onClick = window.open('somepage.jsp')>. She clicks it from one window and it opens with a specific template. she closes the 'opened window' and then switch to the same page with different login and clicks the button. a windows opens but it spots the same template as before !!!. Why is this happening ? I thought that custom tag libraries are thread safe. One possible problem would be that the 'some_template.jsp' came from a bean inside a session. Could a user using two browsers connecting to the same webapp have the same session ? Also this problem so far seems to be limited to her browser, because when I try this out in other computers, they all work fine. Any suggestions ?